Mixing fibrous constituents

ABSTRACT

A method and device for mixing and weighing fibrous material in a weighing cycle includes removing the fibrous material from fiber bales and transporting the fiber material with a feed device into a weighing container. The weighing container is proceeded by a pre-filling chamber that is separated from the weighing container by a controllable flap. After the fibrous material has been weighed, the material is ejected from the weighing container onto a mixing belt. The material feed device is controlled in accordance with a theoretical weight curve that is given for each fibrous material component. Transport speed of the material feed device is varied in accordance with the theoretical weight curve. The theoretical weight curve provides total weight of the transported fibrous material at a given time in the weighing cycle, and is determined for each fibrous material component based on a predetermined relationship of feed rate of the transported fibrous material as a function of time over the course of the weighing cycle in order to achieve a theoretical total weight of fibrous material to be transported into the weighing container during the weighing cycle.

The invention is relative to a method and a device for mixing fibrous[yarn] components by weighing-box feeding provided with a weighingcontainer and a pre-filling chamber. The weighing container is separatedfrom the pre-filling chamber in front of it by a controllable flap andafter the weighing has been completed the material is ejected out of theweighing container onto a mixing belt.

In order to mix fibrous components weighing-box feed devices are usedfor dosing the individual fibrous components in which devices fibrousbales are supplied via a supply table and a subsequent conveyor belt toa rising needle belt from which bales the needle belt loosen out fibrousmaterial in pancakes and transports them upward toward an evener[stripping] roller. A subsequent knock-over roller supplies the materialloosened in this manner to a weighing container.

The weighing of the fibers according to this known, discontinuous methodtakes place as a rule in such a manner that the weighing container isloaded at two different material feed rates with the feed output being afunction of the speed of the needle belt. A coarse dosing takes place atfirst at a high needle-belt speed in order to fill the weighingcontainer in as short a time as possible. However, the desired weighingweight is achieved only inexactly with this high needle-belt speed.Therefore, this rapid filling is carried out only up to a certain degreeof filling. As soon as this first limiting [boundary] value of thecoarse filling has been reached the needle belt is shifted to the lowspeed and the fine dosing follows at this low speed until the desiredfinal weight has been reached. When this second limiting value has beenreached the needle belt is halted. The exact weight is subsequentlydetermined by the balance. It is necessary for an exact determination ofweight that the balance is at a standstill, that is, that it no longermakes any oscillations caused by the filling. This process can requireup to 2 or 3 seconds. The weighing container is emptied thereafter ontoa so-called mixing belt and tared, that is, the weighing device isexactly adjusted to the zero point [to zero]. The weighing apparatus isready therewith for the next weighing and the needle belt is re-engagedin order to carry out at first the coarse filling at a high speed forthe next weighing procedure.

In spite of an exact adjustment of the weighing apparatus and animmediate halting of the needle belt, fibers still fall into theweighing container after the reaching of the second limiting value sothat the desired weighing value is exceeded and occasionally even notreached. This is especially the case if the fibrous material has beenopened only slightly. In order to compensate this impreciseness thisweight value is determined and taken into account as concerns its weightin the further weighings. In addition, flaps are provided above theweighing container that close immediately when the final weight has beenreached in order to avoid a subsequent filling of fibrous material intothe weighing container.

In order to accelerate the weighing cycle a rapid filling of theweighing container is desirable; however, a high needle-belt speed doesresult in a high throughput but the weighing accuracy is low on accountof the poorer opening of the fibrous material since material isentrained and similar events occur. A low needle-belt speed does bringabout a better opening and therewith also a high weighing accuracy butthe throughput and therewith the filling speed of the weighing containeris low. There is therefore the problem of achieving the highest possiblethroughput during the filling and nevertheless achieving a good openingand a high accuracy during the weighing.

Furthermore, the material-specific properties play a great part in theweighing of fibers. Therefore, all speeds and limiting values must beadjusted to these material-specific properties. The loading of thefilling chamber in front of the needle belt also influences theparameters to be adjusted.

As a rule, fiber mixing systems are operated with several weighingcontainers and with different raw materials. The slowest weighingdetermines the throughput of the entire production system. In order toachieve the desired accuracies and throughputs in the described weighingprocess it is necessary that the system is adjusted by operatingpersonnel with a good knowledge of the process and with experience. Theadjustment values must be determined empirically for each fiber type,which is expensive.

Electronically controlled weighing devices are already known thatsignificantly simplify the operation and surveillance of such mixingsystems; nevertheless, it is necessary to input the appropriate data andempirical values for each component to be mixed into the control deviceand to store them there and to retrieve them for the control program forthe materials ready for processing and for the desired mixtures. This istime-consuming and requires experienced professional personnel.Moreover, there is always the danger of erroneous adjustments. Theempirical values have to be tested and determined for new mixtures andmaterials.

DE 34 12 920 teaches a device for dosing filling material for thefilling of packages. The filling of the weighing container takes placein two stages with a coarse dosing and a fine dosing. For the coarsedosing the filling material is conducted via a first feed line into apre-chamber provided with a blocking device against the weighingcontainer. A volumetric measurement of the filling material in thepre-chamber is provided. When the given volume has been reached thefilling of the pre-chamber is terminated and its contents emptied intothe weighing container. After the closing of the blocking member betweenthe pre-chamber and the weighing container the fine dosing takes placevia a second transport stretch. During this time the pre-chamber canalready be re-filled via the first transport stretch so that ashortening of the filling speed for the weighing container occurs. Thisknown device has the disadvantage that two separate filling stretchesare necessary for the fine filling and for the pre-filling so that acorresponding flap control and a corresponding feed device are necessaryfor each filling stretch. The device is therefore relatively expensive.

Furthermore, a method is known for the continuous detection of the bulkweight of granular, fibrous or leaflike material, especially of tobacco,in which the material is delivered in a constant flow by a firsttransport means to a second transport means and supplied from the latterin a mass-constant flow of material to following preparatory operations(DE 28 41 494). The problem in a discontinuous weighing for mixing fibercomponents of nevertheless achieving a continuous transport of materialand an opening of said material is not present in this known device. Theknown method and the device provided for carrying it out are also notsuitable for combining different fibrous components according to givenweight percentages for the further processing.

Finally, U.S. Pat. No. 4,766,966 teaches an electronic control programfor filling a weighing container via a pre-filling chamber in as shorttime as possible but while avoiding excesses of weight caused by therapid filling. The supplying of the material to be weighed into theweighing container is therefore controlled by a differing opening widthof the outlet flap out of the pre-filling container. Nothing can begathered about the mixing of fibrous components and the feed of materialinto the pre-filling chamber from the known device. The control of theejection flap opening entails the danger in the case of fibrous materialthat the material remains hanging on the incompletely opened flaps andthat irregularities and an incomplete filling of the weighing containertherefore occur.

The present invention has the problem of eliminating the citeddeficiencies and of creating a method and weighing device forsignificantly simplifying the adjusting and the dosing of the individualcomponents. A further problem of the invention is to achieve a highproduction output while nevertheless attaining a good opening and a highdegree of weighing accuracy. These problems are solved by the featuresof claims 1,15 and 17 separately or in combination. Further particularsof the invention are described in detail with reference made to thedrawings.

FIG. 1 shows a weighing feeder [automatic hopper-feeder] in a schematicview.

FIG. 2 shows a mixing system with three weighing feeders.

FIGS. 3,4 and 5 show different curves according to which the adjustmentand the control of the system take place.

FIG. 6 shows a comparison of the transported amount with and withoutinterruption of the transport.

FIG. 7 shows a weighing feeder with enlarged pre-filling chamber.

FIG. 1 shows the construction of a weighing feeder in schematic fashion.Bales 1′, 1′, 1′″ are supplied via feed table 2 and its conveyor belt 3to needle belt 4 that loosens pancakes out of the supplied bales andtransports them upward toward evener roller 5. Evener roller 5 ismounted so that it can be adjusted in its interval to needle belt 4 androtates in the direction opposite that of the transport device of needlebelt 4. Fibrous amounts that are too large and rise with needle belt 4are not let through this interval of evener roller 5 but rather areretained by it. As a rule, conveyor belt 3 of supply table 2 and needlebelt 4 are connected to each other by a common drive. Infinitelyvariable drive 41 is provided for needle belt 4 so that the needle beltcan run at every transport speed set by control device 41. Needle belt 4is followed by knock-over roller 6 that rotates at a high speed, beatsthe fibrous material out of needle belt 4 and opens it thereby. Thefibers or fibrous fluff loosened by knock-over roller 6 are transportedinto pre-filling chamber 8 that can be closed by flaps 9 and blocked offfrom weighing container 10. Ventilator 7 assures a suction removal ofdust. Mixing belt 12 runs along and below weighing container 10 ontowhich mixing belt the fibers weighed in weighing container 10 areejected. Pressure roller 11 is arranged at the end of mixing belt 12 forcompressing the fibrous material to a uniform lap [batting] for beingfed into mixing opener 13.

FIG. 7 shows a weighing feeder with enlarged pre-filling chamber 80.Parts of this weighing feeder with the same function as in FIG. 1 arealso designated the same way as in FIG. 1 so that the description of theweighing feeder according to FIG. 1 also applies to FIG. 7. Largepre-filling chamber 80 is arranged above weighing container 10, whichchamber has approximately 80% of the holding capacity of weighingcontainer 10. This enlarged pre-filling chamber serves to receive thematerial delivered during the resting time of the balance and theejecting of the contents of weighing container 10 onto conveyor belt 12so that needle belt 4 can transport fibrous material without standingstill. Measuring devices 13 are arranged on both sides for monitoringthe filling state of the pre-filling chamber.

FIG. 2 shows a system with three weighing-box feeders I, II and III,each of which eject a component onto mixing belt 12. The ejection out ofweighing containers 10 takes place in such a manner that the portions tobe mixed are layered over each other and pass simultaneously to theintake into mixing opener 13. That is, at first weighing feeder IIIejects its component portion onto mixing belt 12, that transports thislayer to weighing feeder II. There, the next component is placed out ofweighing container 10 onto the layer of weighing feeder III and both aretransported further to weighing feeder I, that then places the thirdcomponent onto the two layers. All three layers pass at the end ofconveyor belt 12 under and past pressure roller 11 and are fed to mixingopener 13, that continuously mixes the layer packets and delivers themthough pipeline 14 to a mixing chamber.

The loading of weighing container 10 takes place in the known device insuch a manner that in a first phase the material transport runs rapidlywithout weight control, that is, blocking flaps 9 are closed and thematerial collects in pre-filling chamber 8. During this time the bottomflap of weighing container 10 closes after the ejection of the lastweighing and a taring takes place when the bottom flap is closed. In asecond phase the material transport still runs rapidly and withoutweight control but blocking flap 9 opens and throws the collectedmaterial into weighing container 10, whose bottom flap is closed. In athird phase a filling of weighing container 10 up to a certain fillingamount that is less than the theoretical weight now takes place with arapid transport of material. A signal is initiated that switches thematerial transport to a low speed at which the remaining filling takesplace to the final weight. Once the final weight has been reached thematerial transport is cut off and blocking flaps 9 are closed. A restperiod of approximately 2 seconds to the measurement of the final weighttakes place. Finally, the bottom flap is opened while the materialtransport is still cut off and flaps 9 are closed and the weighedmaterial is ejected onto mixing belt 12.

The pre-filling serves to raise the production output by reducing thestandstill times of the material transport since when blocking flap 9 isclosed in the first two phases the material transport can already startagain. However, the pre-filling function according to the known methodcannot be used if the material transport speed is subject to significantfluctuations.

These disadvantages are eliminated by the method in accordance with theinvention. The supply of material does take place at different speeds;however, it is constantly in operation so that no standstill timesarise. This has the great advantage that as a result of the distributionof the supply of material onto a larger time period that was otherwiseoccupied by the standstill times the work can be carried out at lowermaterial transport speeds that result in a significantly better openingand more precise dosing. An adjusting of the individual parameters iseliminated as further subject matter of the invention since theindividual speeds for material transport and filling including the timeintervals within the weighing cycle optimize themselves [are optimizedautomatically] and adjust simultaneously to the different materials.

The method of operation in accordance with the invention is as follows:

At first, the desired course of a weighing cycle is fixed [retained] ina so-called unit curve. This cycle originated from the sum of manyempirical values and also represents percentage-wise the material feedpercentage-wise [sic] over the time of a weighing cycle subdivided intotime sections. After the needle-belt speed of the weighing feeder isapproximately proportional to the amount of transported material thisunit curve represents in percentage the approximate course of the needlebelt speed and therewith of the material feed or transported amount pertime unit. It was surprisingly determined that the optimal course of thematerial feed speed behaves approximately the same in all instances sothat this curve can be readily transferred in the representation ofpercentage to all concrete values. This has the great advantage that thecourse of the weighing cycle and therewith a significant parameter isentered into control device 40 with the unit curve so that only theweighing time and the final theoretical weight to be observed have to beentered for the concrete individual instance. Of course, a computerintegrated into control device 40 can also determine these two valuesdirectly from the desired production output. Since the filling capacityof weighing container 10 is given, the computer calculates the necessarynumber of weighing cycles and their time as well as the theoreticalweight to be set for each weighing cycle. Using the set theoreticalweight, the computer calculates the theoretical weight curve (FIG. 4)via the unit curve (FIG. 3) according to which theoretical weight curvethe filling of weighing container 10 is controlled via a comparison oftheoretical value and actual value by a corresponding variation of thefiber delivery into weighing container 10. The needle belt speed isadvantageously regulated thereby in such a manner by drive 41 that thestandstill of needle belt 4 does not take place or takes place only inexceptional instances so that the material transport extends over theentire weighing cycle. This is made possible by pre-filling chamber 80(FIG. 7), that is dimensioned to be as large as possible and is at leasthalf as large, in the best instance approximately ⅔ to exactly as largeas weighing container 10 and is therefore capable of receiving acontinuing supply of material even during the resting phase of thebalance and the ejecting of the final weight out of weighing container10. Solely the fine filling amount does not need to be received by thepre-filling chamber since this amount falls directly into weighingcontainer 10 when flaps 9 are open. This achieves not only asignificantly more rapid filling and therewith also a greaterperformance [output] of the weighing feeder but also a better fiberopening and a more exact filling is achieved as result of the nowpossible lesser filling speed. Of course, the saving of the standstilltimes of the material feed can also be utilized to shorten the durationof the weighing cycle and the output can be increased as a resultthereof without the quality of the opening suffering thereby.

The weighing cycle is divided essentially into three phases, namely,(FIG. 6) into pre-filling (zone A), main filling (zone B) and finefilling (zone C). This is augmented by the standstill time (zone D).Given the appropriate size of pre-filling chamber 8 or 80 the mainfilling can be entirely eliminated so that the weighing cycle issubdivided only into pre-filling (zone A+B+C) and fine filling (zone D).The pre-filling takes place with closed flaps 9 in pre-filling chamber 8or 80. During this so-called pre-filling the resting time of the balanceand the measuring of the final weight as well as the opening andejecting of the final weight onto mixing belt 12 including theoptionally necessary taring of the balance take place. The fine fillingalways takes place after the pre-filling chamber has been emptied andwith open flaps 9 in order to bring the balance to the final weight. Inthis manner up to 2 or 3 seconds can be saved, which means a reductionof the transport speed and an increase of performance of 15–25% in acustomary weighing cycle of 12–14 seconds.

FIG. 3 shows the unit curve for a weighing cycle without standstill timeof the material feed. As is apparent from FIG. 3 the transported amountat the beginning of the cycle is approximately 100%. This transportedamount is maintained over approximately 60% of the time of the weighingcycle. The transported amount is then lowered to approximately 20% andthe fine dosing carried out to the final weight for the remaining 20 to25% of the weighing cycle time with a decreasing of the transportedamount. The area under the unit curve represents the total transportedamount to be achieved during the weighing cycle and ejected as finalweight onto mixing belt 12. The theoretical weight curve (FIG. 5)results by integration of this unit curve. The unit curve is fixedthereby for each mixing component I, II and III with 100% representingthe transported amount necessary for achieving the theoretical weight ofthe corresponding component during the weighing cycle time. After [when;since] all three components for the weighing cycle have the same timethe necessary theoretical speed curve is a function of the theoreticalweight to be achieved. Thus, component I has the highest theoreticalspeed, in the example here with 60 m per minute, component II with 30 mper minute and component III with approximately 10 m per minute. Thiscorresponds approximately to the mixing ratio of the components of60:30:10.

However, the control of the mixing process via a theoretical weightcurve derived from the unit curve can also be carried out in thecustomary weighing cycle with standstill of the material transportduring the resting time and the weighing. However, FIG. 6 shows in acomparison what enormous advantages the elimination of the standstilltimes has in favor of a continuous feeding of material. The heavy unitcurve represents the weighing cycle with the customary standstill time.Zone A indicates the customary pre-filling time, zone B the main fillingwhereas zone C indicates the fine dosing and, finally, zone D thestandstill time of the feeding. The percentage numbers indicate acustomary course of the weighing cycle as example. It is immaterialthereby whether the weighing cycle last 12 seconds or 16 seconds. In thepresent instance the example was taken from the weighing cycle of 14.5seconds. As is apparent from FIG. 6 the standstill time is at least[nevertheless] 25 to barely 30%. By avoiding the standstill time for thefeeding of material given an appropriately large pre-filling chamber 80the transport speed can be lowered to approximately 60% or, utilizingthe full transport speed, a shortening of the weighing cycle of 25% canbe achieved. Since the areas under the particular curve represent theamount of theoretical weight, it is clear what an advantage the methodin accordance with the invention offers.

The pre-filling takes place at a material transport speed determined insuch a manner that the available pre-filling chamber 8 or 80 is wellutilized and optimally loaded in the given or available time. If thesize of pre-filling chamber 80 (FIG. 7) is approximately 60 to 80% ofweighing container 10 the essential filling takes place in thispre-filling time. After the opening of flaps 9 this pre-filling amountpasses into weighing container 10 and merely a fine filling at a lowtransport speed is still required in order to exactly achieve thedesired final weight.

The material transport begins with the transport speed (FIG. 4)conditioned by the theoretical weight curve (FIG. 5). A comparison ofthe theoretical/actual values with the given theoretical weight curvedetermines which amount is still to be filled to the final weight. Ifthe differential amount is very great the material transport speed canalso rise again to 100% and be regulated down to the fine transport forthe last 10 or 20%. However, the goal is to carry out the filling withas uniform a transport speed as possible so that the transport speed isalready totally adapted for this pre-filling time in the followingcycle. As soon as the final weight has been reached, flaps 9 close andcut off any further feed of material. However, the transport of materialdoes not cut off but rather immediately begins to fill pre-fillingchamber 8 or 80 again while the balance carries out its resting time andweighing and ejects the weighed material.

In order to make optimal use of pre-filling chamber 8 or 80 it isnecessary to determine the proper speed for the supplying of materialduring this pre-filling period because this speed can deviate from thetheoretical speed (FIG. 4) determined from the theoretical weight curveby virtue of the particularity of the material. This can basically alsobe performed manually and by inputting empirical values. However, it isalso possible that the weighing device optimizes itself here. This takesplace in the following manner:

According to a given basic adjustment the transport of material beginsin the first weighing cycle with a transport speed of approximately 50%.Then, depending on the size of pre-filling chamber 8 or 80, a check ismade after a weighing time of approximately 60% of the weighing cycle tosee what amount of material has passed into pre-filling chamber 8 or 80at the globally adjusted pre-filling speed. This is naturally a functionof the material; however, this dependency on the material isautomatically included in this measuring since the actual amount ismeasured as a function of the transport speed during this pre-filling.

This check can take place in various ways. One method consists, forexample, in that opening blocking flaps 9 causes the pre-filling amountthat had been filled in up to that point to be ejected into weighingcontainer 10 so that the latter can determine an intermediate weightthat is passed on to the computer, that compares this weight with thetheoretical weight. If this actual value is below the theoretical value,this means that the 50% filling speed is too low and must be increasedin accordance with the difference between the actual value and thetheoretical value. The computer sets the proper delivery speed alreadyfor the next weighing cycle so that optimal utilization of pre-fillingchamber 8 or 80 takes place. If the pre-filling amount is too high thespeed is correspondingly lowered. This renders the customary adjustmentmeasures superfluous. This process can also be repeated in order tofine-tune it.

Another way of optimizing the pre-filling speed consists in providingpre-filling chamber 8 with a measuring device for the degree of filling(measuring sound, light barrier, etc.). Pre-filling chamber 8 is filleduntil the measuring device reacts and indicates the filling of thechamber, as a result of which flaps 9 open. At the same time the timerequired is determined and the optimal filling speed is calculated andadjusted therefrom in the computer in that the basic adjustment israised or also lowered. In this method of pre-filling amount cansubsequently be brought to the final weight and utilized as the firstweighing.

In order to avoid an overfilling of pre-filling chamber 8 it ispurposeful to start in the optimization of the transport speed from atransport speed that is so low that the complete filling of pre-fillingchamber 8 or 80 is reliably not yet reached. As a rule this is achievedwith approximately 50% of the transport speed. Then, in the firstweighing cycle the optimal starting speed of needle belt 4 or thetransport speed is determined after approximately 25 to 70% of theweighing cycle time by a comparison of the actual weight with thetheoretical weight, as already described above.

Of course, it can also be provided that the transport speeds determinedfor certain materials and component compositions are stored areretrieved upon a repetition of the same instance without a correspondingoptimization having to be carried out again. However, as a rule anautomatic self-optimization is more advantageous because erroneousadjustments are avoided and the personnel does not have to be concernedwith the adjustment of the proper pre-filling speed.

In the following weighing cycles the optimal transport speed is fixedafter the optimization. As soon as the pre-filling has been achieved thecontrol switches over to the filling speed given by the theoreticalweight curve. The curve is controlled along this curve by a regulatorthat advantageously acts on the delivery speed of needle belt 4 so thata corresponding decrease of the filling speed also occurs in order toperform the fine dosing upon reaching the final weight. As soon as thisfinal weight has been reached the cycle for the material feed is alreadyended and the speed of conveyor belt 4 is switched after the closing offlaps 9 to the optimized transport speed, wherewith the pre-fillingprocess and therewith the new weighing cycle begin. Thus, whilepre-filling chamber 8 or 80 is already being filled with material againthe weighing device with weighing container 10 remains in the restingtime and after this time has elapsed the weighed material is ejected onto mixing belt 12 by opening weighing container 10.

The deviation of the actual weight from the theoretical ejection weightis of course determined even in this weighing process at the end of theweighing cycle and taken into account in the following weighing cycles.This can take place, as his customary, in accordance with the weight;however the transport speed can also be influenced in order to optimizethe procedure. This takes place in such a manner that the course of theweighing cycle remains the same according to the unit curve; however,the calculated correction speed is set equal to 100% of the transportedamount and the setting [indication] of the theoretical weight curve andthe theoretical speed curve derived from it is corrected therewith. Avery precise weighing is achieved in this manner.

As is apparent from FIG. 2, usually several components are to becombined and mixed for the mixture. A weighing feeder I, II or III isprovided for each component. Thus, in the present instance threecomponents can be mixed. Since the individual proportions of thecomponents have different magnitudes the filling of weighing container10 takes different times in the usual known filling methods so that thecomponent that determines the greatest proportion also requires thelongest time so that the two other weighing feeders have terminatedtheir weighing process beforehand and must wait with the ejection oftheir weight amount on the weighing feeder with the greatest amount.According to the invention these three weighing feeders are coordinatedin such a manner with one another as regards their filling speed thatall three weighings are completed at the same time. As a result of thefact that the theoretical weight curve is determined from the unit curvefor each component and given to the particular weighing feeder the speedcurve is correspondingly lowered for the filling speed. The pre-fillingtakes place more slowly, during which, however, the filling to the finalweight can also be retained independently of the pre-filling speed sothat the same time period is filled out as in the case of the largestcomponent. Since the given theoretical weight curve is derived from theunit curve the weighing cycle develops here percentage-wise in the samemanner as in the case of the largest component. A special adjustment isnot required for this. The unit curve is given in each control device orin the control device of the entire system. Thus, only the desiredproduction output or the weighing cycle and the desired final weightsfor the individual components need to be entered. Everything elseincluding the optimization of the process is carried out by the computerof the control.

In order to always have the same mixture at the beginning as well as atthe end of a mixing batch the control can also be programmed in such amanner that the ejection of the weighed fiber amounts beginssuccessively and ends successively so that complete mixture packets arealways produced. In the example of FIG. 2 weighing feeder III willtherefore eject its last weighing [weighed material] onto mixing belt 12and then halt its operation already. The last ejected amount then passesto weighing feeder II, that ejects its component onto this last weighingof weighing feeder III and then also halts its activity. The mixingsystem is not turned off until this mixing packet has also passed thelast weighing feeder I. The start takes place in the same manner in thatweighing feeder III begins and weighing feeders II and I aresuccessively cut in.

In the example described the process control was described by setting[indicating] a desired theoretical weight curve according to which thefeeding of material into weighing container 10 is controlled. Thistheoretical weight curve can also be determined empirically; however, itis advantageous to determine it in accordance with the invention via theunit curve.

The optimizing of the transport speed, especially for the pre-filling,is significant not only in conjunction with the larger pre-fillingchamber 80, that can receive practically the entire filling amount up tothe residual filling for the fine dosing. Enlarged pre-filling chamber80 can also be successfully used in the traditional, known weighingprocesses and significantly shorten the process and lower the requiredtransport speed.

As is apparent from FIG. 6 from the continuous heavy curve it isabsolutely possible to indicate a unit curve even for the traditionalweighing process with standstill (area D) to [of] the material transportand to control the cycle in accordance with it.

Thus, these parts of the invention acquire independent significance;however, the optimum is achieved by using all these described partstogether. The described embodiments are only exemplary and can be variedin various ways or combined in a different manner without departing fromthe concept of the invention.

1. A method for mixing fibrous components by means of weighing feedingin a weighing cycle wherein the fibrous material to be dosed is removedfrom fiber bales and transported by a material feed device into aweighing container preceded by a pre-filling chamber, which weighingcontainer is separated from the pre-filling chamber by a controllableflap, and after the weighing has taken place the material is ejectedfrom the weighing container onto a mixing belt, characterized in that adesired theoretical weight curve is given for each fibrous component toa respective weighing device according to which curve the material feedfor filling the weighing container during the weighing cycle iscontrolled by appropriately varying the transport speed, saidtheoretical weight curve providing total weight of the transportedfibrous material at a given time in the weighing cycle and is determinedfor each fibrous material component based on a predeterminedrelationship of feed rate of the transported fibrous material as afunction of time over the weighing cycle to achieve a theoretical totalweight of fibrous material to be transported into the weighing containerduring the weighing cycle.
 2. A control device for controlling thetransport speed of a material feed device of a weighing feed device formixing fibrous components in which the fibrous material to be dosed istransported by the material feed device into a weighing container duringa weighing cycle, characterized in that a desired theoretical weightcurve is entered into the control device for the fibrous material to bedosed according to which curve the control device controls the materialfeed device for the filling of the weighing container by varying thetransport speed, said theoretical weight curve providing total weight ofthe transported fibrous material at a given time in the weighing cycleand is determined for each fibrous material component based on apredetermined relationship of feed rate of the transported fibrousmaterial as a function of time over the weighing cycle to achieve atheoretical total weight of fibrous material to be transported into theweighing container during the weighing cycle.
 3. The method according toclaim 1 characterized in that the duration of the weighing cycle is thesame for the individual components.
 4. The method according to claim 1characterized in that the weighing cycle is subdivided into apre-filling phase during which the transported material is caught in apre-filling chamber and into a fine filling phase during which thetransported material passes through the pre-filling chamber directlyinto the weighing container.
 5. The method according to claim 1characterized in that the variation of the material feed takes place byaltering the transport speed of a needle belt that transports thefibrous material to the pre-filling chamber.
 6. The method according toclaim 1 characterized in that the adaptation of the actual weight to thetheoretical weight given by the theoretical weight curve takes place bymeans of a regulator.
 7. The method according to claim 6 characterizedin that the regulator influences transport speed of a needle belt thattransports the fibrous material to the pre-filling chamber.
 8. Themethod according to claim 1 characterized in that the time of theweighing cycle is determined by the speed of the mixing belt.
 9. Themethod according to claim 1 characterized in that the ejection of theweighed amounts of fiber onto the mixing belt begins successively andends successively so that complete mixing packets are always produced.10. A method for mixing fibrous components by means of weighing feedingin which the fibrous material to be dosed is removed from fiber balesand transported by a material feed into a weighing container preceded bya pre-filling chamber, which weighing container is separated from thepre-filling chamber in front of it by a controllable flap, and after theweighing has taken place the material is ejected from the weighingcontainer onto a mixing belt, characterized in that a desiredtheoretical weight curve is given for each fibrous component to arespective weighing device, according to which the material feed forfilling the weighing container is controlled by appropriately varyingthe transport speed, such that in order to determine the optimaltransport speed the transport speed of the material feed is adjusted forthe first weighing cycle after the setting of an empirical value andafter about 25 to 70% of the weighing cycle time the actual valuereached is compared with the theoretical value and the differencedetermined in this manner is utilized to correct the transport speed ofthe material feed.
 11. The method according to claim 10, characterizedin that the empirical value for the optimization of the transport speedis approximately 50%.
 12. The method according to claim 10 characterizedin that the transport speed remains unchanged for the fine dosingindependently of the changing of the transport speed for the materialtransport during the pre-filling and/or main filling.
 13. A method formixing fibrous components by means of weighing feeding in which thefibrous material to be dosed is removed from fiber bales and transportedby a material feed into a weighing container preceded by a pre-fillingchamber, which weighing container is separated from the pre-fillingchamber in front of it by a controllable flap, and after the weighinghas taken place the material is ejected from the weighing container ontoa mixing belt, characterized in that a desired theoretical weight curveis given for each fibrous component to a respective weighing deviceaccording to which curve the material feed for filling the weighingcontainer is controlled by appropriately varying the transport speedsuch that at the end of the weighing cycle the deviation of the actualweight from the theoretical ejection weight is determined and thedifference is taken into consideration for the correction of thetransport speed.
 14. A method for mixing fibrous components by means ofweighing feeding in which the fibrous material to be dosed is removedfrom fiber bales and transported by a material feed into a weighingcontainer preceded by a pre-filling chamber, which weighing container isseparated from the pre-filling chamber in front of it by a controllableflap, and after the weighing has taken place the material is ejectedfrom the weighing container onto a mixing belt, characterized in thatthe material feed transports fibrous material during the entire weighingcycle as the loading of the weighing container takes placediscontinuously.
 15. The method according to claim 14 characterized inthat the transport speed of the material feed drops towards zero towardthe end of the fine dosing but the full transport speed is reassumedimmediately after the closure of the blocking flaps.
 16. A weighing feeddevice in which fibrous material to be dosed is transported by amaterial feed device into a weighing container preceded by a pre-fillingchamber and in which the weighing container is separated from thepre-filling chamber by a controllable flap, characterized in that thematerial feed device is associated with a control device that controlsthe transport speed of the material feed during a weighing cycle inaccordance with a given theoretical weight curve, said theoreticalweight curve providing total weight of the transported fibrous materialat a given time in the weighing cycle and is determined for each fibrousmaterial component based on a predetermined relationship of feed rate ofthe transported fibrous material as a function of time over the weighingcycle to achieve a theoretical total weight of fibrous material to betransported into the weighing container during the weighing cycle. 17.The device according to claim 16 characterized in that the material feeddevice comprises a needle belt that loosens fibrous material out of thesupplied bales and is provided with an infinitely variable drive. 18.The device according to claim 16 characterized in that the holdingcapacity of the pre-filling chamber corresponds to the holding capacityof the weighing container.
 19. A method for mixing fibrous components bymeans of weighing feeding in which the fibrous material to be dosed isremoved from fiber bales and transported by a material feed into aweighing container preceded by a pre-filling chamber, the holdingcapacity of which is approximately 80% of the holding capacity of saidweighing container, said weighing container being separated from thepre-filling chamber in front of it by a controllable flap, and after theweighing has taken place the material is ejected from the weighingcontainer onto a mixing belt, characterized in that a desiredtheoretical weight curve is given for each fibrous component to arespective weighing device according to which curve the material feedfor filling the weighing container is controlled by appropriatelyvarying the transport speed.
 20. The method according to claim 19characterized in that the holding capacity of the pre-filling chamber isat least the holding capacity of the weighing chamber minus the amountof fine filling.
 21. A control device for controlling the transportspeed of a material feed device of a weighing feed device for mixingfibrous components during a weighing cycle in which the fibrous materialto be dosed is transported by the material feed device into a weighingcontainer characterized in that the desired theoretical weight curve isentered into the control device for the fibrous material to be dosedaccording to which curve the control device controls the material feedfor the filling of the weighing container by varying the transportspeed, said theoretical weight curve providing total weight of thetransported fibrous material at a given time in the weighing cycle andis determined for each fibrous material component based on apredetermined relationship of feed rate of the transported fibrousmaterial as a function of time over the weighing cycle to achieve atheoretical total weight of fibrous material to be transported into theweighing container during the weighing cycle.